A communication network transfers information, such as voice, video and telemetry, among the User Equipment (UE) of subscribers. Information, such as broadband Internet data, broadcast services, and network control data, can be transferred between the network itself and the subscriber UEs. A number of existing networks, such as Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (3rd Generation cellular/radio technology) (CDMA2000), and Worldwide Interoperability for Microwave Access, Inc. (WiMAX), according to the IEEE 802.16 wireless broadband standard, support parallel operation of a plurality of such information services. For such support, and for optimization of the network capacity, these networks must be able to transfer information at rapidly changing data rates. The networks must also be able to combine the different services into a single physical data stream, used to transfer the combined information over the physical channel.
The Transport Layer typically combines data of different rates. The combination of information services and data rates changes rapidly. Thus, the transmitter must notify the receiver of the change at high rates. Most systems attach an additional header to transmitted data, describing the service combination format and data rates of the currently transferred data. This addition, naturally, increases the overhead.
In WCDMA (UMTS), for example, each service is related to a transport channel (TrCH). The service combination and data rate selection format used to combine the TrCHs into a physical data stream coded composite transport channel (CCTrCH), is referred to as a transport format combination (TFC). A transport format combination indicator (TFCI) is attached to each frame of data to indicate which the TFC that was selected. The receiver uses the TFCI to select the format for the decoding and separation of data into the different services. This process is referred to as TFCI signaling.
A number of techniques have been proposed or suggested for conserving the bandwidth required for TFCI signaling. For example, a Blind Transport Format Detection (BTFD) method was introduced in “Multiplexing and Channel Coding (FDD),” 3rd Generation Partnership Project, Technical Specification Group Radio Access Network, 3GPP TS 25.212 V4.5.0 (2002-06). The disclosed Blind Transport Format Detection method detects the TFC with a blind algorithm.
A Blind Transport Format Detection method must perform three types of TrCHs detection, namely, single, explicit, and guided transport channel format detection. A single transport format detected TrCH has a transport set not containing more than one transport format with more than zero transport blocks and that does not use guided detection. The transport format with more than zero transport blocks must have CRC with non-zero length. Energy detection and a cyclic redundancy check (CRC) are used to blindly detect the transport format transmitted by the single transport format detected TrCH when this TrCH is the only TrCH of the CCTrCH.
Explicit and guided transport format detected TrCHs are non-signaled TrCHs that have more than one transport format and do not use single detection. An explicitly detected TrCH must have at least one block transmitted every Transmission Time Interval (TTI). Each block of an explicitly detected TrCH is appended with a non-zero CRC. Guided detection is used on a TrCH with zero length CRC that is associated with an explicitly detected TrCH. By detecting the transport format of an explicitly detected TrCH, the transport format of the associated guided detected TrCH is also decided.
In order to perform explicit and single detections, CRC is checked for all possible transport format combinations. A valid TFC (transport format combination) is selected if the CRC was valid for all TrCHs in the CCTrCH using this combination. This technique, however, can introduce a misdetection of the TFC, since statistically, CRC checks of all TrCHs may be erroneously valid for a TFC that was not transmitted. A need therefore exists for a Blind Transport Format Detection method that avoids the misdetection problem.